A microassay technique for measuring immunological activity has been developed based on the incorporation of radioactive nucleotides into lymphocyte DNA. This allows study of multiple samples of cells taken from patients with a variety of diseases, or from experimental animals. It is not uncommon for several hundred samples per day to require assay of radioactive incorporation into samples which are harvested onto filter discs, often referred to as "dot-blots". The major limitations in the application of this technique result from the requirement to cut individual dot-blots from a multi-sample filter, transfer them to vials, add the hazardous, solvent-based, scintillant counting-fluid to each vial, cap, number and finally effect a radiation count of the individual samples using a scintillation counter. Thus this technique is extremely time consuming and involves the use of hazardous material.
An alternative method involves the use of photographic film for mapping. The principal advantages of this method, namely that photographic film is inexpensive and the spatial resolution obtained is excellent, are outweighed by the disadvantages which are that the technique is relatively insensitive because exposure times are measured in days, only limited quantitation can be obtained and even that involves the use of expensive instruments, and the technique is extremely time consuming.
Thus there is a long-felt need for a method and apparatus for the simultaneous counting of multiple samples on single filters by direct counting of radioactive emissions, so avoiding the shortcomings of the multiple sample handling and the use of the scintillation counting technique, and the photographic technique. Accordingly, this is the objective of the present invention.